A journal of HW and SW hackery

Archive for June, 2010

First off, the boards I mentioned in the previous post come tomorrow, so if you’re lucky I may get in 3 posts in less than a week, but this is completely unrelated.

Some background …

Here’s the deal. I recently got an Avocent SwitchView IP 1010 for less than $100. Great deal. The previous owner mentioned that it was missing a cable, but no real issue because that just meant that local access to the console/PC wouldn’t be available; accessing the PC over IP would of course still work and that’s what I wanted anyway… it turns out that was kind-of true; if you use the IP KVM with the vga+usb cable to the PC (which is what the PO supplied) you can access it over IP and all is well–if you are ok with providing mouse/keyboard to the PC via USB. What I found tonight was that if you want to connect the PC to the KVM via PS/2, you need the “KVM cable that shipped with the unit” and had an end for connecting to the “Computer” port.

Cutting to the chase

Ok, so that was confusing. If you happen to have this SwitchView unit and you’ve lost the cable that plugs into the “Computer” port and splits that output into the keyboard and mouse PS/2 inputs to the PC you’re connecting the KVM to, you know why this is a problem and this write-up is for you.

If you’re a fan of just getting the specifics and not getting any fancy details, look no further than the following table:

“Computer”

8-pin mini-din

pins

Keyboard PS/2

pins

Mouse PS/2

pins

1 (kbd data)

1

2 (mouse GND)

3

3 (kbd clk)

5

4 (kbd +5V)

4

5 (mouse data)

1

6 (kbd GND)

3

7 (mouse clk)

5

8 (mouse +5V)

4

If you think I got pins 2 and 6 backwards, feel free to swap them, the GNDs are connected, so it’s no big deal. If you read on, you’ll see why I picked them…but now that I’ve put them in the table like that, I’m tempted to change my mind as well. FWIW, I just finished determining these connections about an hour ago and I haven’t tested a complete cable. I’m missing the 8-pin mini-din (thought I had an old VGA card splitter cable that had the mini-din on it, but pins were connected somehow internally so it didn’t work) and so I’ve ordered 11 from jameco.com (part# 111878). In the meantime, I took the PS/2 cable off of an old keyboard and poked the wires into the connector to setup the keyboard and mouse separately and (tested separately) both the mouse and keyboard work. That said I’m 100% confident of the connections above, just waiting for the part to complete my own cable.

The details

Of course I opened up my SwitchView IP 1010. Here’s a pic of the bottom, focused on the “Computer” connector:

First thing was to determine which of the pins in the group of 8 was connected to which pin in the connector. The pattern is:

(5)

(2)

(1)

(3)

(8)

(7)

(4)

(6)

Next step was to figure out which pins could be determined using a continuity test. This revealed that pin 8 was connected to the +5V on the mouse PS/2 port and pin 4 was connected to the +5 on the keyboard PS/2 port. Pins 2 and 6 were found to be connected to GND.

(5)

Gnd

(1)

(3)

Mou+5

(7)

Kbd+5

Gnd

Flipping the board over, you can see the following pic:

Looking for a way to determine which of the remaining pins were clk and data, I noticed the 2 ICs directly above the connector. Testing revealed that pins 7 and 3 were each connected to the right lower leg of one of these parts labeled KDA/P7. I couldn’t find this part in a quick search, but it seemed to make since that perhaps this was a clock circuit? Still not sure, but noticed 2 of the same KDA/P7s, 1 each, near the PS/2 ports. In both cases, the right lower leg was connected to the clock line on the PS/2 ports. That’s good enough for me, and leaves the remaining 2 pins as the data pins. So now we have the following:

data

Gnd

data

clk

Mou+5

clk

Kbd+5

Gnd

I chose to believe the layout guy picked this arrangement and grouped the pins like so:

data

Gnd

data

Clk

Mou+5

clk

Kbd+5

Gnd

That would put the right group of 4 pins as the keyboard PS/2 connection and the left group of 4 pins as the mouse PS/2 connection. After listing the pins in the table above, though, I think that the layout guy just got stuck with something that made sense numerically and I just got lucky because the grounds are connected!

Either way, this seems to test out. I’ll try to remember to update the post once I get my 8pin mini-din and can test both the keyboard and mouse simultaneously, but I can’t see any reason why it wouldn’t work. Since I’ll be cutting the PS/2 cables off of an old keyboard and mouse and the Jameco part costs $0.89 when purchased in Qty’s of 10, this cable will cost $0.89– assuming I can figure out a way to get my money out of the remaining 10 connectors I ordered. I tend to over-order; the minimum $10 purchase and the cost of shipping gets me buying more than I need. So to rephrase, the cable will cost me $10.

ok, so it’s been awhile since my last post. I’m likely to say this many times, but I have great aspirations of blogging regularly and then it just never happens. I’ve started writing “Hard Drive Repair by Removing and Replacing the Head” and taken pics of many more of my HW repairs but just haven’t given myself the time to do the repairs and write about it. I repaired the master volume potentiometer on our Clavinova CLP100 last weekend using a similar part (not pin compatible, however) from Digikey and completely forgot to take any pictures, so that won’t be coming to this page, either.

Next week, however, I hope to have my first PCB back from the fine folks at BatchPCB.com (well, now, I haven’t seen my PCBs, so I might change my mind about them!)… and I intend to do a write-up on it.

I’ve got a few kids in the house and I use my garage as my “lab”. Most of the tools I’ve got are pretty safe, but I’ve got a few soldering irons and a heat gun that could be dangerous toys if they were to be used absent of any adult supervision. The PCB I’ve got coming is a shield for an Arduino that adds a 12-key keypad, dual 7-segment display, and connections for up to 4 125V/15A relays. I’ve got a first run of the code completed and what I’ll have when I put it all together is something much like the security control one of the big home improvement stores puts on their saws or bolt-cutters they use in-store.

I’ll post pics and an update when the stuff comes in. I may even have an extra board or two if all goes well.